The present invention relates to a system for detecting load on an engine driven generator in which the load is detected in accordance with output voltage.
In a load detecting system provided in an engine driven generator such as a generator described in Japanese Utility Model Application Laid-Open 59-2937, voltage produced in a main coil circuit is transferred through a current transformer, for detecting the load on the generator.
However, as shown in FIG. 8, a phase difference .theta. between current I and voltage V in the main coil occurs because of the load in the coil circuit. Consequently, active power (shown by hatched zone) reduces. The active power Ta produced in the main coil circuit with respect to apparent power T (=V.times.I) generated by the generator is EQU Ta =V.times.I.times.cos.theta.
Consequently, reactive power dependent on power factor cos.theta. generates. For example, if the power factor cos.theta. is 0.7, the current transformer detects only the output of 14A, in spite of the output of 20A in the main coil.
Because of such a detected small output, an operator determines that the generator has a spare output sufficient to bear a further load. However, the maximum output is produced in the main coil, and a further loading exceeds the capacity of the generator, which will cause failure such as engine stall.
In order to eliminate this disadvantage, it is considered to provide a power-factor indicator. However, the indicator is expensive and large in size, and hence the manufacturing cost increases and the generator becomes large in size.